Implantable medical electrical leads are well known in the fields of cardiac stimulation and monitoring, including neurological stimulation and cardiac pacing and cardioversion/defibrillation. In the field of cardiac stimulation and monitoring, endocardial leads are placed through a transvenous route to position one or more sensing and/or stimulation electrodes in a desired location within a heart chamber or interconnecting vasculature. During this type of procedure, a lead is passed through the subclavian, jugular, or cephalic vein, into the superior vena cava, and finally into a chamber of the heart or the associated vascular system. An active or passive fixation mechanism at the distal end of the endocardial lead may be deployed to maintain the distal end of the lead at a desired location.
It is highly desirable that implantable leads have the lowest possible profile while the insulation maintain sufficient integrity to electrically isolate one or more conductors of the leads over the life of the implanted lead.